The present invention generally relates to a rotating disk storage device and a pivot bearing assembly. The invention relates more particularly to a pivot bearing assembly that pivotably supports, within a disk enclosure, an actuator head suspension assembly for moving a magnetic head above a magnetic disk. The invention relates also to a rotating disk storage device using the pivot bearing assembly.
A magnetic disk device as a rotating disk storage device includes a magnetic disk, an actuator head suspension assembly, and a control unit. The magnetic disk has a magnetic layer formed on a surface thereof and spins about a spindle shaft. The control unit controls data read/write operations and operations of the actuator head suspension assembly.
The actuator head suspension assembly is mounted with a magnetic head for reading and writing data and a slider for providing an air bearing surface (ABS). The actuator head suspension assembly also includes a carriage arm that pivots about a pivot shaft.
A coil support is formed in part of the carriage arm. The coil support holds a voice coil. The coil support is disposed in a magnetic field of a voice coil magnet. The voice coil magnet and the voice coil form a voice coil motor (VCM) that generates a driving force for pivotally moving the carriage arm.
When the magnetic disk spins, a surface air flow forms an air bearing. This gives the air bearing surface of the slider an ascending force, causing the slider to fly just above the magnetic disk surface. The driving force of the voice coil motor causes the slider to pivot about the pivot shaft substantially radially relative to the magnetic disk. While pivotally moving, the slider maintains a position slightly above the magnetic disk surface. The slider thus allows the magnetic head to position at a desired radial location on the disk surface for reading/writing data.
The actuator head suspension assembly of the magnetic disk device must be accurately controlled for positioning the magnetic head that reads data from and writes data onto the magnetic disk. The actuator head suspension assembly is mounted on the pivot shaft by way of a pivot bearing assembly that pivotally moves accurately about the pivot shaft.
The following bearing assembly is proposed as a pivot bearing assembly achieving the aforementioned purpose. This specific bearing assembly includes a body, a bearing head, and a central recess (see, for example, Japanese Patent Laid-open No. 2000-36163 (pp. 4 to 5; FIGS. 3 to 5)). The body has a cylindrical portion having a first outer diameter. The bearing head has a cylindrical portion having a second outer diameter that is relatively larger than the first outer diameter of the body. The central recess is defined between the body and the bearing head. This bearing assembly is mounted to a pivot bearing housing of a shoulder structure having a first nominal inner diameter and a second nominal inner diameter that is smaller than the first nominal inner diameter.
Another type of the pivot bearing assembly is proposed. This pivot bearing assembly is arranged as follows. Specifically, there is provided a two-stage shaft having a large-diameter shaft portion and a small-diameter shaft portion. An inner raceway for a lower row is directly formed on an outer periphery of the large-diameter shaft portion. An outer raceway is directly formed on an inner peripheral surface of a sleeve outer race that surrounds the large-diameter shaft portion of the two-stage shaft. A plurality of balls for the lower row is disposed between the inner raceway and the outer raceway. A ball bearing thus formed has a lower end surface of the outer race pressed tightly up against an upper end surface of the sleeve outer race. The inner race of the ball bearing is secured to the small-diameter shaft portion with an appropriate preload applied from an upper end surface side of the inner race (see, for example, Japanese Patent Laid-open No. 2003-77237 (pp. 3 and 4; FIGS. 2 to 4)).
Still another type of the pivot bearing assembly is proposed. Referring to FIG. 6, a pivot unit 50 is proposed (see, e.g., Japanese Patent Laid-open No. 2003-239985 (p. 3; FIG. 1)). The pivot unit 50 includes a rotary shaft 51, and a housing 52 rotatably mounted thereto by way of two radial ball bearings 50A, 50B disposed vertically at upper and lower positions of the rotary shaft 51. A protrusion 52a is formed on an inner periphery of the housing 52. The protrusion 52a keeps the two radial ball bearings 50A, 50B away from each other vertically.
A further type of the pivot bearing assembly is proposed (see, e.g., Japanese Patent Laid-open No. Hei 5-205413 (p. 6; FIG. 3)). This pivot mechanism includes the following components: a pivot shaft; a lower ball bearing assembly and an upper ball bearing assembly that are first mounted to the pivot shaft and then secured in position; and a steel sleeve having a central hole therein, in which the lower ball bearing assembly and the upper ball bearing assembly are disposed and secured in position. For each of the lower ball bearing assembly and the upper ball bearing assembly, an inner race has been preloaded toward each other and an outer race has been preloaded away from each other.
A rotation transmission apparatus is also proposed (see, e.g., Japanese Patent Laid-open No. Hei 5-149353). In this apparatus, a plurality of roller bearings incorporating rolling elements of varying pitch circle diameters is disposed in tandem. A retainer of each of the rolling elements of the roller bearings is connected to each other.